Four different scaling methods are used to scale a coarse-grained soil into a grading with smaller particles. The methods are mixing method, scalping method, equal-weight replacement method and similar grading method. The biggest grain size of each soil after grading is 10 mm, 20 mm, 40 mm and 60 mm, respectively. A number of relative density tests are conducted. To further analyse the test results, more relative density for other three soils with arbitrary grading are performed. The maximum and minimum dry density tests are carried out using vibrating method and loose filling method. The relationship between maximum or minimum dry density and the soil grading parameters, maximum particle size is investigated under the same compactive effort. A normalizing method is presented to express the relationship between dry density and grading. The relationship of dry density versus Cu, Cc and maximum particle size is found. According to the relation, the maximum dry density of the real gradation can be determined.
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For the Three Gorges granite, a finite difference software package FLAC is used to study failure process of heterogeneous rock material. Firstly, proper scale of finite difference grids is under consideration with scanning electron microscopy photo of the granite. Based on mineral components identification results of the granite and fuzzy clustering method, the actual image data are transformed into the finite difference grid by applying image processing techniques. A convenient and efficient two-dimensional numerical modeling method for heterogeneous geomaterials is presented. Furthermore, shear bond propagation and failure process of the granite are simulated in uniaxial compression test based on experimental strain soft model; and stress concentration phenomena are analyzed. Finally, numerical simulation of granite samples under different triaxial compression tests is studied. The results show that the numerical modeling method based on digital image processing can be used to calculate the mechanical responses of geomaterials by taking their heterogeneities into considerations.
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Seismic response of rock is the main topic in current dynamic analysis of underground structures, but the dynamic response and collapse mechanisms of rock structures are lack of thorough study. Based on a practical hydropower project, three kinds of unfavorable geological structures are selected in the dynamic analysis of large underground caverns by using block theory. Then ground deformation history and characteristics of open and slip joints are studied under seismic loadings by a discrete element program UDEC. Simultaneously the movement mechanisms of the cutting blocks are also analyzed. The results show that steep dip geological structures have greater impact on earthquake response of underground caverns. Under the seismic loading, adverse geological structures slip along the steep incline joint with sudden. Collapse form of adverse geological structures may change with seismic load increasing.
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A new kind of true triaxial apparatus is introduced. To simulate the loading process of core wall element under the dam construction process, true triaxial tests on clay mixed with gravel soil were carried out under complex stress state, which can simulate the practical stress path to some extent. It was found that even for single axial load applied from the major principal stress direction, because of the influence of initial complex stress state, the stress induced anisotropy effects are remarkable. There are different relationships between stress and strain in different principal stresses directions. Based on the testing results, it is suggested that when carrying out the numerical analysis of dam, the stress induced anisotropy should be taken into consideration, so as to reasonably describe the practical behaviors of the core and the whole dam body under three dimensional complex stress states.
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